Learning Forum

[Jindrich]

Hello, I am having an issue with simulating the 2D turbine linear blade cascade using FLUENT 2023R1. As there is a supersonic exit velocity with shock-waves, I require a non-reflecting boundary condition. Currently, I am using a steady state implicit density-based solver and compressible ideal gas model with a general NRBC. However, the static pressure at the pressure-outlet boundary condition is deviating considerably from the desired value and is not remaining constant. I have tried using both pressure at infinity and average pressure boundary specifications, as well as adjusting the sigma1 and sigma2 constants, but have not found a solution.

Is there any trick to make the NRBC keep the constant outlet pressure?

[Essence]

Hello,

Can you share the model screenshot of the same?

[Jindrich]

Hello,

this is the screenshot of the computational domain. I had to obscure the blade profile as I can not share it. Is that what you mean?

[Essence]

Hello,

Please refer to the links provided: https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v231/en/flu_ug/flu_ug_bcs_sec_nrbc.html?q=non%20reflecting%20boundary

https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v231/en/flu_ug/flu_ug_boundary_conditions_task_page.html?q=non%20reflecting%20boundary

[Jindrich]

Thank you, I am aware of these references, however, if I set the general NRBC as stated there, the outlet pressure is deviating considerably from desired value and is not even remaining constant.

[Essence]

 

Hello,

I think you might be facing convergence issues. Please try using lower URFs and initialize using Hybrid initialization. Try to use first order spatial discretization and once fully converged, then opt for higher order. Check if the mesh at the outlet is proper or not.